1. Field of the Invention
This patent application is for an apparatus and method for injecting a concentrated fluorescent dye into a sealed air-conditioning system prior to the system going into service.
2. Description of the Related Art
The Montreal Protocol, the Kyoto Protocol and environmental pressures have resulted in the prohibition against the venting of air-conditioning refrigerants into the air. As a result, air-conditioning systems have become much more efficient and lighter. These smaller air-conditioning systems have very critical charges of refrigerant. Because of the higher efficiency and reduction in size, the system charge of refrigerant has been reduced by about 50% (approximately 500 grams or less of refrigerant compared to a typical 1 kg charge of 10 years ago). Future systems will have even smaller and more critical charges probably around 100-200 grams.
Detecting leaks in air-conditioning systems has become of paramount and key importance for vehicle manufacturers in order to keep customers comfortable and to reduce warranty costs. With more and more vehicle manufacturers wanting to install detection dyes in the air-conditioning systems at their factories, pressure to reduce the costs have been placed on the detection industry.
Leak detection, materials detection and qualitative non-destructive testing are well suited to techniques employing fluorescence detection. These techniques rely upon the unique physical property of various materials to fluoresce when excited by certain wavelengths of visible or ultraviolet (UV) light.
It is a well-known phenomenon that electromagnetic energy within the near ultraviolet spectrum of approximately 315 to 400 nanometer wavelengths produces fluorescence in certain materials. That is, the fluorescent materials absorb radiated energy at the near UV or blue wavelengths and re-radiate or emit it at a longer wavelength in the visible spectrum. Thus, when fluorescent material absorbs electromagnetic energy in a specific excitation frequency band in a specific wavelength range, the material can emit electromagnetic energy in a characteristic fluorescent emission frequency band within the visible light spectrum. This phenomenon has enabled inspection and detection techniques in which fluorescent dyes, inks or pigments are illuminated by lamps selectively filtered to emit only ultraviolet radiation (invisible to the human eye) and then re-radiate with a high luminescence in the visible spectrum.
For example, the slow leakage of refrigerant from an air conditioning system is difficult to locate by any other means. The reason for the difficulty is because the refrigerant escapes as an invisible gas at such a low rate with rapid diffusion that the concentration of refrigerant in air near the leak site is difficult to differentiate from that surrounding any other location along the system circulation lines. However, by infusing into the circulating system a small amount of fluorescent dye that is soluble in the refrigerant, the dye is carried out of the system with the refrigerant and glows brightly at the leak site when the area is swept with a UV lamp (see, for example, U.S. Pat. No. 5,357,782, U.S. Pat. No. Re. 35,370, U.S. Pat. No. Re. 35,395, and U.S. Pat. No. 5,681,984).
A similar procedure can be used to locate leaks of other fluids, such as lubricants, oils, fuels, heat transfer fluids or hydraulic fluids. Other UV inspection techniques use fluorescent dyes or paint to detect fissures or stress cracks in structural members.
Some dyes are most concentrated in a powder form. Each different type of dye medium that is produced obviously adds cost and volume to each application. Typically, the automotive detection industry uses napthalene or naphthalamide. For example, the dye may be Fluorescent Yellow 43. The dye powder is blended into a solution using aromatic solvents and non-solvent lubricants so that the dye is more easily injected and can be quickly taken into solution with the refrigerant lubricant in the system. This solution is better suited for the after market and service sectors for its ease of installation.
Another concern is the time that it will take for enough of the dye to be in circulation so that the vehicle manufacturer can detect any leaks within a short period of operation (one minute or less) at the completion of the assembly process. Two factors in this time problem are the insertion location for the dye and the physical form, i.e., liquid, powder, solid, swatch, capsule, etc., of the dye which effects the ability to dissolve the dye into the circulating refrigerant and oil mixture solution of the air-conditioning system. The desired insertion location for the dye is near the compressor or the high-pressure side of the system (see FIGS. 1 and 2). These locations will offer the most heat and turbulence that will facilitate rapid dissolution of the dye into the refrigerant, thereby allowing near instant leak detection.
The typical dye application is done when the air-conditioning system is charged with refrigerant and lubricant mixture. The dye is usually in a blended solution with lubricant and is injected against the pressure of the static refrigerant system (see, for example, U.S. Pat. Nos. 5,699,678, 5,826,636 and 6,050,310). These methods and associated apparatuses are fine for after market and field service repairs but are time consuming and not cost effective at the automotive manufacturing level.
There has been some application of dye at the automotive manufacturing level. For example, U.S. Pat. No. 5,650,563 discloses a method for installing a concentrated dye, using a liquid dye that is absorbed into a swatch. The cost of this method is problematic. First, a dye powder must be formulated into a solution. There are costs associated with the swatch and the labor to install the dye onto the swatch. In addition, there are problems associated with the physical size for shipping these products, handling of the swatch and the limited areas of an automotive air-conditioning system where the swatch can be installed. In addition, the swatch must be installed in a low-pressure component, e.g., accumulator or filter, of the system.
Furthermore, this method takes a longer time for the dye to go into solution, thus meaning a longer time to run on the assembly line before leaks can be detected. Moreover, this process is not conducive to automation and requires operators to manually insert the swatches or wafers into a system component before assembly.
The goal of the present apparatus and method is to have a dye material fixed to an interior wall or component of the system so that the dye can be installed by a tier 1 or tier 2 supplier of parts or components to the vehicle assembly plant. The present invention uses a more concentrated dye powder without any additional or formulating materials added. For example, a one pound cube of dye will be enough dye for over 2000 vehicles. The present method will keep down the production costs and will result in simpler freight handling for each customer. The powder can be preformed or melted into solid blocks or capsules to simplify handling and inventory.
The present application discloses an apparatus and a method for injecting a concentrated fluorescent dye into a sealed air-conditioning system prior to the system going into service. The apparatus comprises a heated reservoir, where a concentrated fluorescent dye is melted to form a concentrated liquid fluorescent dye; a heated hose, wherein the heated hose has a first end and a second end and where the heated reservoir is connected to the first end of the heated hose; and a heated injector, where the heated injector is connected to the second end of the heated hose.
In preferred embodiments of the apparatus, the heated reservoir has a temperature between 150xc2x0 C. and 205xc2x0 C., the heated hose has a temperature between 160xc2x0 C. and 210xc2x0 C. and the heated injector has a temperature between 160xc2x0 C. and 210xc2x0 C. In a more preferred embodiment, the heated reservoir is sealed within a nitrogen blanket.
In other preferred embodiments, the apparatus further comprises a microprocessor to precisely control the timing and volume of injection, a sensor, i.e., optical, proximity, contact, magnetic or microswitch, for preventing injection outside the desired component and a manual trigger for injecting the liquid fluorescent dye.
In yet other preferred embodiments, the heated injector is air assisted and has a spray pattern selected from the group consisting of a stream, a spray and combinations thereof.
The method for injecting a concentrated fluorescent dye into a sealed air-conditioning system prior to the system going into service comprises heating a fluorescent dye to form a liquid fluorescent dye; maintaining the liquid fluorescent dye at a constant temperature and viscosity; and injecting the liquid fluorescent dye into a component of a sealed air-conditioning system prior to the system going into service.
In preferred embodiments of the method, the heating step is performed in a heated reservoir having a temperature between 150xc2x0 C. and 205xc2x0 C., the maintaining step is performed at a temperature between 150xc2x0 C. and 210xc2x0 C. and the injecting step is performed at a temperature between 160xc2x0 C. and 205xc2x0 C.
In more preferred embodiments of the method, the heated reservoir is sealed with a nitrogen blanket, the injecting step is performed with a heated injector that has a spray pattern selected from the group consisting of a stream, a spray and combinations thereof and the heated injector is air controlled.
In other preferred embodiments of the method, the injecting step is controlled by a microprocessor and is initiated by applying a physical force to a manual trigger.